The Parrot uses a single (3.8V) 70 mAhr cell that is semi-permanently affixed to the altimeter. The USB interface for the Parrot charges it whenever it's plugged in.

The deployments require a separate user-supplied battery. For that job I use a second 70 mAhr cell, with the cell protection circuitry removed, to both do the deployments and power a Beeline transmitter. I put a remove-before-flight wire between the altimeter power screw switch and the arming screw switch to charge up the deployment battery in parallel with the Parrot's battery.

The cell internal resistance for these tiny cells is so low that it provides significantly more current than necessary for Estes ignitors, despite being only 3.6-4.2 volts. All I have ever used for deployments (in my admitedly short deployment career) is a single Li-poly cell, and charges made from Estes ignitors potted inside small cardboard tubes with Pyrodex in the middle and 5-minute Epoxy at both ends. Never had a misfire.

What are you planning to use for charging the cells?
Do the cells have built-in charge protection circuitry? If so, they may cut off the current if they sense a short, and a current pulse of 3-4 Amps for a deployment charge would usually qualify as something that a cell protection circuit on a 100 mAhr cell would respond to. A 1-second pulse of 3-4 Amps wouldn't even warm the cells up appreciably, so you don't need the cell protection circuitry for that. But if you do remove the protection, you're one step closer to causing a fire if you hook up the wrong charger. The cell specs I have seen say that they are safe (though permanently damaged) with a continuous hard short across the terminals.

A two-cell battery should work for both applications, as long as the cells are charged up for the RRC2. When the cells are fully charged, each cell will be at 4.1V. At about 60% discharge, they will still be about 3.5V. I might be a little concerned about the current you could get through a 1-Ohm ignitor with 2 Li-poly cells in series. It could be 7-8 Amps, (vs about 3 Amps for a 9V battery or 3 Amps for a single Li-Poly cell), so check the max current specs for the altimeter. If the altimeter has inputs for separate batteries for the deployment charge and the altimeter power, don't hook up 1 Li-poly cell to one and a 2-cell Li-poly battery to the other one, unless you know for sure that the there is no possible current path that could charge the single-cell battery from the 2-cell battery.

The HA uses a pass through setup that fires the igniter directly from the battery. The RRC uses capacitance IF I remember correctly. But, I'm not using LiPo on the RRC.... In fact, my dual deploy bird will use an RRC and a PF HA45 for redundancy, both will be off 9V batteries. Only the HA in the min diameter birds will get the LiPos.

As for charging, I have a high dollar setup with a balanced charge unit and temperature sensor. I can even hook up the balancer w/o the charger and balance cells. I run RC Crawlers, desert racers and street racers on LiPo, so the charger was a must....

I'm using e-matches for my igniters, they seem to fire at a pretty low amperage. I set one off on Saturday by accident when I tested the continuity using my Estes remote. The remote may have been hot enough to give it full current when I put the key in, but, who knows. 😳

Are your cells bare, or do they have cell protection circuitry built in? If they have the protection circuits, you would need to watch out for the protection circuits cutting off the current and starving the Hi-alt's power supply when you fire the charge. But if the ematch resistance is high enough, and if the Hi-alt has a good capacitor to keep its own power up during the discharge, then it could work o.k. with or without the cell protection in place. I would recommend doing a test with your batteries, Hi-Alt 45k and other switches, etc. in a flight-like configuration, except put 2 ematches together in parallel. If they burn o.k. and the altimeter stays powered, then you know your setup will have some margin when you do it for real.

Also, can you turn down the current on your RC battery charger? If you blast the little tiny cells with a really high charge current you can damage them. You'll want to keep the current down around 50-100 mA for the 100mAhr cells.

I already cut the CPs off.... I'm going to put them together today if I have time out here.

Oh yeah, this charger is basically a computer system. I can do anything I want. It also has a temperature monitor and 9 set memories for my different batteries. It even does automatic motor break-ins. I have 9 RC cars/trucks/crawlers that I am changing all over to LiPos. One even runs dual battery packs an RX pack and dual motors/speed controls.

This is my 2.2 class crawler.